Police and the labour ministry are investigating the incident, which reportedly involved suffocation in a testing chamber.

The workers are reported to have died of suffocation. Police are investigating the incident at the plant in the southeastern city of Ulsan, which is Hyundai's biggest manufacturing facility.

Three workers died at a Hyundai car plant on Tuesday, the South Korean automaker told AFP, with local reports suggesting it was an accident during a vehicle performance test. "The three -- two Hyundai researchers and the other affiliated with a subcontractor -- were found collapsed at a test chamber of the plant where they were conducting a car performance test,

Police said three researchers died at a Hyundai Motor factory in Ulsan on Tuesday. According to the Ulsan Metropolitan Police Agency, the 112 police hotline received a report on 3:19 p.m. that three researchers who were conducting a chamber test for the electrified vehicle division in factory No.